Study: Muscle wasting occurs rapidly in critically ill patients

Critically ill patients in a recent study lost muscle mass rapidly while being cared for in the ICU.

“Survivors of critical illness experience significant skeletal muscle weakness and physical disability, which can persist for at least five years,” Zudin A. Puthucheary, MRCP, of University College London, and colleagues wrote in the background of the article. “Muscle wasting contributes substantially to weakness acquired in the intensive care unit, but its time course and underlying pathophysiological mechanisms remain poorly characterized and not well understood.”

Previous studies have shown a link between immobility and decreased protein synthesis, but these studies did not have standardized time points to compare muscle measurements, according to a news release. Puthucheary and colleagues designed their study to define the roles of protein synthesis and breakdown during critical illness and to study the time course for acute muscle loss.

The study, which was published Oct. 9 in JAMA, included 63 critically ill patients who were prospectively recruited within 24 hours of ICU admission at a university teaching hospital and a community hospital in England from August 2009 to April 2011. The average age of participants was 54.7, and 59% were male. Researchers determined muscle loss using serial ultrasound measurement of the rectus femoris cross-sectional area on days one, three, seven and 10. They also measured muscle protein synthesis and leg protein turnover in some of the participants.

The researchers found a 17.7% reduction in the rectus femoris cross-sectional area at day 10. Patients who had experienced multiorgan failure showed a larger decrease in muscle compared with patients who experienced single organ failure — a loss of 15.7% vs. 3% by day seven, and a loss of 8.7% vs. 1.8% by day three.

Their findings also showed that patients’ muscle protein synthesis fell to levels equivalent to the healthy fasted state on day one. It increased to rates similar to the healthy fed state by day seven, but it wasn't enough to prevent net muscle loss.

“Importantly, these overall effects occurred despite the administration of enteral nutrition,” the authors wrote. “Unexpectedly, higher protein delivery in the first week was associated with greater muscle wasting. ... This finding is in keeping with an adverse effect of early targeted feeding, which is supported by the observation that a short period of continuous amino acid feeding reduces muscle protein synthesis.”

Further study is needed to determine the best timing and mode of nutritional support, the authors wrote. “Early interventions to enhance anabolism may be required in addition to those aimed at reducing catabolism if muscle wasting is to be limited or prevented,” they added.